Nematode resistant grape rootstock &#39;9365-85&#39;

ABSTRACT

Rootstock ‘9365-85’ is a cross of L514-10 ( Vitis rufotomentosa× ( V. champinii  ‘Dog Ridge’× V. riparia  ‘Riparia Gloire’))× V. champinii  c9038. This invention relates to a new and distinct variety of grape rootstock with resistance to a broad array of soil-borne nematodes including root-knot, dagger, lesion and citrus nematodes. The variety is moderately susceptible to ring nematode, but has strong resistance to grape phylloxera.

BOTANICAL/COMMERCIAL CLASSIFICATION

L514-10 (Vitis rufotomentosa×(V. champinii ‘Dog Ridge’×V. riparia‘Riparia Gloire’))×V. champinii c9038.

VARIETY DENOMINATION

‘9365-85’.

BACKGROUND OF THE INVENTION

Nematodes are important pests in vineyards around the world, and thesesoil-borne pests can be particularly problematic in Californiavineyards. Two factors intensify the impact of nematodes—the high valueof grapes and of vineyard land. These factors force growers to ignorethe steps of leaving land fallow and rotating crops, both of whichreduce nematode build up and delay the selection of adapted strains.Nematicides and fumigants help control nematodes, but the use of thesepesticides has been greatly restricted and their future use in doubtbecause they must be persistent and penetrate deeply through the soilprofile to be highly effective. In addition, grape rootstocks were bredto resist grape phylloxera (a devastating root-feeding aphid), and werenot selected for nematode resistance. The grape rootstocks Freedom andHarmony were released by the USDA/Fresno to provide resistance tonematodes, but they are not resistant to grape phylloxera. Morerecently, McKenry at UC Riverside released two rootstocks, RS3 and RS9(siblings of a Schwarzmann×Ramsey cross), designed to resist multiplenematode species and provide growers with nematode resistant rootstockalternatives. However, they have nematode resistance from a relativelynarrow genetic base, which may promote the evolution of strains capableof feeding on them. Therefore, there is a need to develop nematoderesistant grape rootstock.

BRIEF SUMMARY OF THE INVENTION

This invention relates to a new and distinct variety of grape rootstockwith resistance to a broad array of soil-borne nematodes includingroot-knot, dagger, lesion and citrus nematodes. It is moderatelysusceptible to ring nematode, but has strong resistance to grapephylloxera. It is a cross of L514-10 (Vitis rufotomentosa×(V. champinii‘Dog Ridge’×V. riparia ‘Riparia Gloire’))×V. champinii c9038. It isrecommended for vineyard sites with severe nematode infestations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: number of ring nematodes recovered off rootstock selectionsgrowing in 1 gal pots with three soils collected from the GalloLivingston Ranch, known to have severe and chronic nematode pressure.Results per soils are means of three replicate pots.

FIG. 2: a photograph showing rootstock ‘9365-85’.

DETAILED DESCRIPTION OF THE INVENTION

A breeding program was initiated in 1990 at UC Davis to provide a groupof rootstocks with broad and durable resistance to the nematodes foundin California vineyards. This program commenced with an evaluation ofselections that remained from breeding efforts in the late 1960s andearly 1970s. These selections from the late 1960s and early 1970s werepreviously screened against two root knot nematode species (Meloidogyneincognita acrita and M. arenaria thamsei), the lesion nematode(Pratylenchus vulnus), and the dagger nematode (Xiphinema index). In1990, these selections were evaluated for their ability to root and forgrowth habits such as brushy growth, internode length and the degree oflateral shoot production. In 1993 and 1994, the best of these selectionswere crossed to species chosen for their ability to reduce scion vigoror improve the rooting of the progeny. The parentage and speciescomposition of the 8905-05 and other crosses are listed in Table 1.About 5,000 progeny were planted in the vineyard and their evaluationfor nematode resistance was initiated in 1996.

The first phase of the selection process examined the progeny for theirgeneral vigor and horticultural characters such as internode length andthe degree of lateral shoot formation. The best 1,000 progeny, selectedfrom a large number of, were advanced to a rooting assay. Ten 2-nodedormant cuttings of the best 1,000 were taken in December 1996 andtested for their ability to form roots. Rootstocks that root wellgenerally graft well, thus this evaluation was a key indicator of theirfuture success as rootstocks. One hundred of the progeny were selected,again with an effort to get a broad representation from the large numberof families.

The second phase of the selection process involved testing these 100selections for resistance to M. incognita 13. This root-knot nematodeisolate is capable of feeding on many rootstocks, but does not feed onrootstocks that derive their resistance from V. champinii (Freedom,Harmony, Dog Ridge and Ramsey). All of the nematode testing in thisbreeding program utilized potted plants under greenhouse conditions withoptimized soils and irrigation techniques to promote nematode feeding.Resistance to this isolate of root-knot nematode was evaluated byassaying the number of galls on the roots after inoculation with 1,000J2 larvae (the free-living infectious stage of this nematode).Resistance was also evaluated by extracting the J2 nematodes in the potsafter the root galls were counted. Later phases of the root-knotnematode screening evaluated resistance by counting the number of eggmasses formed using a technique developed in the Walker lab (Cousins andWalker 2001 Plant Disease 85:1052-1054). There were no root galls on 33ofthe 100 selections and the 33 selections were advanced to the nextphase of screening.

The third phase of the selection process tested the 33 root-knotnematode resistant selections against two aggressive strains ofroot-knot nematode and against the dagger nematode, X. index. The twoaggressive strains were selected in the Walker lab from soils providedby McKenry, from a declining Harmony vineyard. Root-knot nematodes wereextracted from this soil and the larvae were placed onto tomato plantswith high susceptibility to root-knot nematodes. Two egg masses werecollected from these infested plants and J2 larvae from each mass wereput on a separate uninfested tomato plant to create new strains from asingle egg mass (root-knot nematodes are parthenogenic). These newstrains were multiplied on tomato and were then used to inoculate pottedplants of Harmony rootstock to verify their ability to feed aggressivelyon this resistant rootstock. These two strains were named HarmA andHarmC. Later investigations determined that HarmA was a strain of M.arenaria while HarmC was a strain of M. incognita. The dagger nematodeswere collected from several vineyards in the Napa Valley of California,which were known to have fanleaf degeneration.

The 33 selections were then inoculated with each of the three nematodestrains independently. The root-knot nematode screens used 1,000 J2larvae to inoculate plants growing in 1,000 cm³ plastic pots with acoarse sand/clay loam soil mix. The dagger nematode screens were done inthe same pots and soils, but used 200 adult X. index as the inoculum.Fourteen selections did not produce egg masses when inoculated with thethree root-knot nematode strains nor did they produce root tip gallsafter inoculation with X. index (Table 2).

In the fourth phase, the 14 selections were subjected to a series oftests. The first was a combined inoculum of all four nematodes at onceto determine the impact of simultaneous nematode feeding on resistance(Table 3). They were also tested against the four nematodes over a rangeof temperatures, 24, 27, 30 and 32° C. There was some erosion ofresistance to HarmA (the most aggressive strain of root-knot nematode)at this temperature, but 6 of the selections performed very well (Table4). Root-knot nematode resistance is known to fail at about 28° C. in awide range of species including tomato, pepper and plum. The 14selections were also evaluated for resistance to lesion (Pratylenchusvulnus), citrus (Tylenchulus semipenetrans) and ring (Mesocriconemaxenoplax) nematodes (Table 3). From this series of tests a number of sixrootstock selections were made, including 9365-85. A summary of the9365-85 characteristics is presented below.

Grape phylloxera are capable of feeding and producing galls (nodosities)on the young roots of virtually all grape rootstocks and species. Inorder to gauge the phylloxera hosting ability of the final sixselections, they were tested for the ability to support phylloxera onnodosities and compared to a set of commercial rootstocks. Three sets ofyoung root pieces from each selection were inoculated with 10 phylloxeraeggs collected from 101-14 Mgt rootstock roots. Over a 21-day period,the number of eggs and juveniles that were produced were summed anddivided by 10 (the original inoculum) to produce the average rate ofincrease. Table 5 presents these results for the six selections.Nodosity galling on young roots does not appear to damage grapevines,only feeding and galling on mature roots (tuberosities) leads to vinedeath. The high rate of phylloxera feeding, galling and reproduction on101-14 Mgt (7.98 average rate of increase) has been observed in pasttests. Most of the values were very low, although this 101-14 Mgtstrains is well adapted to 9407-14. Three of the selections were veryresistant: 8909-05, 9363-16 and 9449-27. The low values for AXR#1demonstrate that the results of this test do not reflect field level ortuberosity level feeding and damage, and that phylloxera adaptindependently to rootstock hosts.

It will take years to determine which sites each of these rootstockselections are best suited to, but they have unparalleled levels ofresistance to nematodes and should excel in sites with single and mixednematode species infestations. Four of the selections (9365-43, 9365-85,9407-14 and 9449-27) were grafted to Fiesta Seedless and planted in aFresno rootstock trial in 2004. That year two of these selections(9365-43 and 9365-85) were also included in a Chardonnay rootstock trialin Santa Maria. The six rootstock selections in large pots using soilsfrom the Gallo Livingston Ranch where nematode pressure from root-knot,lesion, ring and Xiphinema americanum, is known to be severe andchronic. This test was conducted to evaluate these selections under“field conditions” using infested soil without added inoculations. Allof the selections performed very well against root-knot nematodes (Table6) and two, 9407-14 and 8909-05, also performed very well against ringnematode (FIG. 1).

DETAILED BOTANICAL DESCRIPTION

Rootstock 9365-85 is a staminate flowered vine with leaves that appearmore like V. riparia with longer teeth, more prominent lobing, andthinner more puckered texture. Its resistance to root-knot and daggernematodes in the combined testing was very good, and it resists citrusand lesion nematode, but is susceptible to ring nematode (Table 3).9365-85's resistance to M. arenaria HarmA was the most severely impactedby higher temperatures compared with the other five selections, althoughit is not statistically different from 9365-43 and 9363-16 (Table 4).9365-85 is an excellent mother vine with long canes, good internodelengths and few lateral shoots. Preliminary propagation results indicateit has moderately deep rooting angles.

The following is a further description of rootstock ‘9365-85’:

Shoot tips—The variety has shoot tips which are enclosed in expandingleaves, green and sparsely covered with arachnose tomentum.

Young leaves—The variety has young leaves which are green, three lobedglabrous leaves with fine arachnose tomentum and relatively long sharplypointed teeth.

Mature leaves—The variety has mature leaves which are dark green,slightly 3-lobed, broad cuneiform-shaped leaves with medium-sizedangular to convex teeth, and medium-sized petioles. The upper surface isglabrous, broadly rugose with some indented puckering near the petiole.The lower surface has scattered arachnose tomentum, fine bristles alongthe main vines and small tufted bristles (domatia) at the intersectionof the main veins. The petiolar sinus is a narrow U to lyre shape.

Canes—The variety has dark brown canes with long internodes andrelatively limited lateral development, nodes have short pointed buds.Canes are oval in cross-section, have thin diaphragms and medium sizedpith.

Flowers—The variety has flowers which are staminate.

TABLE 1 Parentage of the five nematode resistant grape rootstockselections. Selection Parentage 8909-05 V. rupestris × M. rotundifolia9363-16 (V. rufotomentosa × (V. champinii ‘Dog Ridge’ × Riparia Gloire))× Riparia Gloire 9365-43 (V. rufotomentosa × (V. champinii ‘Dog Ridge’ ×Riparia Gloire)) × V. champinii c9038 (probably V. candicans × V.monticola) 9365-85 (V. rufotomentosa × (V. champinii ‘Dog Ridge’ ×Riparia Gloire)) × V. champinii c9038 (probably V. candicans × V.monticola) 9407-14 (V. champinii ‘Ramsey’ × Riparia Gloire) × V.champinii c9021 (probably V. condicans × V. berlandieri)

TABLE 2 Selections with broad resistance to four nematodes wheninoculated individually. M. M. in- incognita M. arenaria − cognita −Selection X. index 13 HarmA HarmC 8909-05 R R R R 9317-06 R R R R9332-43 R R R R 9344-03 R R R R 9363-16 R R R R 9365-43 R R R R− 9365-62R R R R 9365-85 R− R R R 9403-35 R R R− R− 9403-107 R R R R 9407-14 R RR R 9449-23 R R R R 9449-25 R R R R 9449-27 R R R R Control Group: 1616CS R R− R− Harmony S R S S Colombard S S S S R = Resistant, no gallsymptoms or egg masses observed R− = Trace infection S = Susceptible,symptoms present, nematode reproduction supported

TABLE 3 Summary results for 14 nematode resistant selections when testedagainst combined inoculum with three root-knot nematode (RKN) strainsand dagger nematode (Xi). Results of testing against citrus, lesion andring are also reported. RKN Egg Xi Galls in Masses in Combined CombinedGenotypes Testing Testing Citrus Lesion Ring 8909-05 R 0 R O R <100 R<10 R <1,000 9317-06 MS <1 S <5 R <100 R <50 HS <20,000 9332-43 S <5 S<5 R <100 R <50 S <10,000 9344-03 S <5 MS <1 S >400 S <200 S <10,0009363-16 R 0 R 0 S >400 R <50 S <10,000 9365-43 R 0 R− <1 R <100 R <50 MS<5,000 9365-62 MS <1 S <5 R <100 R <50 MS <5,000 9365-85 MS <1 R− <1 R<100 R <50 S <10,000 9403-107 R 0 S <5 R <100 R <50 MS <5,000 9403-35 S<5 S <5 R <50 MS <5,000 9407-14 R 0 R 0 R <100 R <50 LS <3,000 9449-23MS <1 R 0 R <100 R <50 S <10,000 9449-25 MS <1 R 0 R <100 R <50 S<10,000 9449-27 MS <1 R− <1 R <100 R <50 S <10,000 1616C S >50 S <5S >400 S <200 HS <20,000 Freedom S >10 S <10 R <100 R <50 HS <20,000Colombard S >100 S >100 S <1000 S <300 HS <30,000 Harmony S >10 S <50 S<1000 S <200 HS <30,000 St. George S <100 S <50 S >400 R <50 S <10,000

TABLE 4 Number of egg masses per potted plant and per gram of root afterinoculation with 1,000 M. arenaria HarmA nematodes and testing at 32° C.Egg Mass/g Genotype Egg Mass/Plant Root Colombard 442.50 a 155.86 aHarmony 156.00 b 123.28 b 9365-85 32.25 c 16.49 c 9365-43 7.25 c 6.04 cd9363-16 6.75 c 5.74 cd 9449-27 0.25 c 0.22 d 9317-06 0.00 cc 0 d 8909-050.00 c 0 d

TABLE 5 The average rate of population increase of phylloxera onnodosities formed on young root tips of advanced rootstock selectionsand a set of standard rootstocks. The phylloxera were selected from avineyard planted on 101-14 Mgt rootstock. 8909-05 0.59 9363-16 0.899365-43 1.86 9365-85 1.99 9407-14 9.83 9449-27 0.30 1103P 2.10 101-14Mgt 7.98 Teleki 5C 1.38 AxR#1 2.15 O39-16 0.43

TABLE 6 Number of root-knot nematode egg masses recovered from rootstockselections growing in 1 gal pots with soild collected from sites at theGallo Livingston vineyards. This vineyard is known to have severe andchronic nematode pressure. Results per soild are means of threereplicate pots. Selection Soil 1 Soil 2 Soil 3 Colombard 69.02 89.8 74.6Harmony 31.2 0 2.8 St. George 9.8 26.2 16.0 9365-85 1 0 1.4 9407-14 0 00 9363-16 0 0 1.4 9365-43 0 0 0.2 9449-27 0 0 0.8 8909-05 0 0 0

1. A novel and distinct variety of grape rootstock designated 9365-85having the characteristics described and illustrated herein.